Vignette: 44 year old male presented with chronic right lower quadrant abdominal pain. Temperature, urinalysis & CBC were all normal.

Imaging Findings:
This coronal lower abdominal CT with oral contrast & IV contrast shows a focal calcification consistent with appendicolith at the appediceal-cecal junction. The appendix wall is thickened and dilated up to 10 mm with paucity of intraluminal air and oral contrast. No drainable fluid collections are seen to suggest abscess collection. Periappendiceal fat stranding is not definitively present but in this patient, there is a lack of significant intraabdominal fat which slightly decreases the prominence of fat stranding. Findings are most consistent with diagnosis of appendicitis.

Anatomy of the Appendix:
The appendix attaches to the cecum at the base of the free taenia in the lower right quadrant of the abdomen. The appendix can be found in any position relative to the cecum, but most common positions are the pelvic & retrocecal positions (95% of cases). It has a hollow lumen, lymphoid-filled walls and usually measures <6mm diameter.

Appendicitis:
Appendicitis occurs when the appendiceal lumen becomes blocked. Blockage can occur from lymphoid hyperplasia, neoplasia, fibrosis, appendicolith (calcified deposit) or a foreign object. Over time, the blocked appendix becomes filled with mucus, increasing the intraluminal pressure and leading to thrombosis of small vessels. The resulting ischemia will cause necrosis and bacterial overgrowth. If untreated, perforation and/or abscess formation can occur.

Radiographic Findings:
Ultrasound, plain film and CT can all be used to visualize the appendix; however, CT provides the best specificity (94%) and sensitivity (95%) in diagnosing appendicitis, and is recommended for diagnosing lower right quadrant pain in adults when clinical examination is inconclusive. In patients who are children and appropriate body habitus, ultrasound is preferred method to minimize exposure to ionizing radiation.

On CT, as discussed in this vignette, findings include:
• Appendix diameter > 6 mm
• Appendiceal Wall enhancement with IV contrast
• Infiltration of peri-appendiceal fat (inflammatory fat stranding)
• Appendicolith (~30% of cases): if present, may be asymptomatic or symptomatic and can occur in both acute and chronic appendicitis; is a highly specific finding (can also be seen on plain film radiography on KUB)
• Cecal apical thickening
• Adjacent bowel wall thickening
• Abscess

*Chronic appendicitis may be characterized by the presence of an appendicolith and an enlarged appendix without any other radiographic findings. Appendicoliths may be difficult to distinguish from contrast media and are better visualized on reformatted bone or lung windows.

Differential Diagnosis:
Appendiceal neoplasms can mimic appendicitis. Included in the differential diagnosis of appendicitis are:
• appendiceal carcinoma
• lymphoma
• mucocele (mucinous cystadenoma / mucinous cystadenocarcinoma).

Other conditions of the cecum and pelvis may present with bowel wall thickening, fat stranding or abscesses and similar clinical symptoms.

References:
Giuliano V et al. Chronic appendicitis “syndrome” manifested by an appendicolith and thickened appendix presenting as chronic right lower abdominal pain in adults. Emerg Radiol. 2006 Mar;12(3):96-8.

Ives EP et al. Independent Predictors of Acute Appendicitis on CT with Pathologic Correlation. Acad Radiol 2008; 15:996–1003.

Gluecker TM et al. Diseases of the cecum: a CT pictorial review. Eur Radiol (2003) 13:L51–L61.

Case Vignette authored and created by C. Westra (radRounds Radiology Network) and peer-reviewed by medical educational board of radRounds.

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